Sorry about that. The backend that generates the alerts was hung. FWIW, we had it running on a shared machine for a while, but that's not working anymore (for reasons). I'm (part-time) working on getting it back up. I've fixed one issue so far, but there's at least one more problem before it'll be back up and running somewhere other than local workstations.
In the meantime, if it appears to be down in the future and I'm not around, you can try running it locally:
1. Get an infra checkout with "fetch infra" (this is fast)
2. cd infra/infra
3. git pull && gclient sync
That will generate the alert json and upload it to sheriff-o-matic. sheriff-o-matic just reads that json and generates the UI from that.